Field of the Invention
The present invention relates to fluid bearings having bearing pads, and more particularly, to bearing pads configured to facilitate cooling of the bearing pad.
Description of Related Art
Certain bearings provide an interface between a rotating structure and a contact surface. Hydrodynamic bearings are such that the rotating element (such as a shaft) rides on an oil film between the shaft and the bearing. Shearing of the oil causes the heat to build. The top surface of the bearing facilitates the formation of the oil film or wedge. During operation there should be no physical contact between the two. Journal bearings provide lift to essentially counter external forces including but not limited to gravity, aerodynamic forces such as unbalanced steam forces (in the case of steam turbines), and gear loads for bearings supporting gears and allow the shaft to rotate. Thrust bearings are bearings that deal with axial thrust.
One problem encountered with bearings is the build-up of temperature of the bearing components, including the bearing pads. Temperature of the bearing pads can rise to harmful levels under high speed or load conditions. The temperature may not rise to the same temperature across the entire bearing pad, and in many bearing pads, it has been determined that the trailing edge side of the pivot rises to particularly high temperatures.
Oil can be provided to the bearing, to assist in cooling the bearing pad and the other components of the bearing. Many prior art bearing pads are made of solid metal, which, as previously described, get hot under high speed and load conditions. While the oil can directly contact the surface of these solid bearing pads to aid in cooling the bearing pad, none of the metal beneath the surface is able to be in direct contact with the cooling oil.
Several U.S. patents, including U.S. Pat. Nos. 3,814,487; 5,222,815; 5,556,208; 6,588,933; and 6,746,152, have a duct or passage which allows oil to flow internally through a bearing pad. However, these prior art bearing pads can be mechanically weakened by the ducts or passages that run internally through the bearing pads. Additionally, these prior art bearing pads do not provide the flexibility to optimize the flow pattern of the oil through the bearing pad to more efficiently cool the bearing pad, but, instead, treat the whole bearing pad evenly.